摘要
Charge separation and transformation are some of the key requirements for high-efficiency photocatalysis. The photocatalytic reaction mechanism provides a guideline for the development and commercialization of high-efficiency photocatalysts. In this study, we designed and favorably synthesized BMO@BOC heterojunctions via a facile solvothermal route and applied the heat treatment method for application in high-efficiency photocatalytic NO removal. More importantly, both continuous stream and intermittent stream methods with in situ diffuse reflectance infrared Fourier transform spectroscopy were applied to intuitively and dynamically investigate the adsorption process and oxidation process of NO removal over the photocatalyst surface. The intermediate products(NO-, NO2-, and NO2) were explicitly detected in both the adsorption process and oxidation process, whilst the final product(NO3-) appeared only in the oxidation process, owing to the separation, migration, and conversion of photoinduced electron-hole pairs.
电荷分离及转移是影响光催化效率的重要因素之一.本文采用简易的水热焙烧法,设计并构筑了Bi2Mo3O12@Bi2O2CO3(BMO@BOC)异质结,促进了光生载流子的分离与迁移,并优化了异质结构中的BMO与BOC的组分比例,其中BMO@BOC-1样品展现了最高的光催化脱除NO效率(~35%),且具有优异的循环稳定性.SEM与TEM结果表明,BMO@BOC-1样品是由超薄纳米片构成,可以提供丰富的反应活性位点,从而促进光催化反应的发生.HRTEM,XRD及Raman充分证明已成功合成不同组分比例的BMO@BOC异质结.同时, Raman与XPS结果表明, BMO@BOC异质结由Bi, O,C及Mo组成, XPS图谱中拟合峰位置的偏移是由异质结组分不同所致.值得注意的是, UV-visDRS结果表明,BMO@BOC-4具有最好的光谱吸收性能,但它与BMO@BOC-2和BMO@BOC-1样品的吸收带边相近,而PL结果则表明BMO@BOC-1具有更好的电荷分离性能,以及合适的组分比例,在一定程度上可以促进光吸收,并能最大限度的促进光生载流子的分离.BMO@BOC-1样品的ESR测试结果说明,·OH与·O2-的含量随着光照时间的延长而增加,证实了它们是光催化NO氧化的活性中间物种.另外,光催反应机制的研究在高效光催化剂的研发及其商业化应用中具有深远意义.本文还利用原位红外实时动态监测手段,采用"连续流测试法"与"间歇流测试法"直观动态地研究了BMO@BOC异质结催化剂表面光催化NO脱除反应过程.结果表明,在开灯前的吸附阶段于催化剂表面形成了NO-, NO2-以及NO2等中间产物,开灯后的氧化阶段出现终产物(NO3-).进一步深入分析,中间产物NO-和NO2-在氧化阶段会被氧化活性物种进一步氧化成NO3-,而中间产物NO2可能作为一种毒副产物影响NO的完全氧化.综上所述,本文将为理解NO氧化过程提供直观且动态的研究方法,对光催化技术的发展具有重要的指导意义.
基金
supported by the Fundamental Research Funds for the Central Universities(2018CDYJSY0055)
the National Natural Science Foundation of China(21576034)
Joint Funds of the National Natural Science Foundation of China-Guangdong(U1801254)
the project funded by Chongqing Special Postdoctoral Science Foundation(Xm T2018043)
Technological projects of Chongqing Municipal Education Commission(KJZDK201800801)
the Innovative Research Team of Chongqing(CXTDG201602014)~~
